Experimental Animal Nutrition
Objectives : Exosomes are endogenous nanoparticles that participate in cell-to-cell communication through the transfer of cargos such RNAs, lipids and proteins from donor cells to recipient cells. Previously, we showed that mammals absorb exosomes from milk. Ultrasonication causes a transient disruption of the exosome membranes, leading to loss of microRNAs. When mice were fed diets based on the AIN-93G formulation, modified to contain a physiological amount of milk exosomes (exosome and RNA-sufficient diet, ERS) or sonicated exosomes (exosome and RNA-depleted diet, ERD), we observed a loss of circulating and tissue microRNAs and phenotypes such as aberrant purine metabolism. The objective of this study was to conduct a comprehensive analysis ofthe effects of sonication on exosomes cargos and bioavailability, thereby generating insights into mechanisms through which ERD elicits phenotypes.
Methods : Exosomes were isolated from ultrasonicated (USE) and non-sonicated (NSE) bovine milk by ultracentrifugation and authenticated following guidelines of the International Society for Extracellular Vesicles. MicroRNAs were analyzed by small RNA-sequencing. Lipids and proteins were analyzed by LC/MS-MS. Intestinal transport was assessed using FM 4-64-labeled exosomes in primary human small intestine cells (FHs cells). Bioavailability of exosomes transfected with IRDye-labeled miR-320a was assessed using oral gavage in C57BL/6 mice.The unpaired t-test was used for statistical analysis P< 0.05 was considered statistically significant.
Results : Ultrasonication affected the vesicle count and exosome morphology. Western blot analysis detected marker proteins only in NSE. The content of microRNAs was about 93% lower in USE than NSE. Significant difference was noted for lipid and protein identities between NSE and USE. Reduced uptake of USE by intestinal cells and loss of cargo accumulation in murine livers and pancreas for USE compared to NSE (Fig.1-5).
Conclusions : Ultrasonication causesa loss of microRNAs in milk exosomes. The unique patterns of proteins and lipids likely is due to an exchangeof membranes between exosomes and other vesicles during ultrasonication, which might explain the lower bioavailability of USE compared to NSE. We currently test the exchange of lipids during ultrasonication.
Funding Sources : NIFA, NIH, Gates Foundation,PureTech, Inc. and USDA Hatch and Multistate. J.Z. is a consultant for PureTech.